Safety switch

ABSTRACT

Operating means for the operating of a switch ( 2 ) in an electric current circuit, comprising an inner cylinder ( 6 ) connected to the switch, with a push rod ( 7 ) axially displaceable in the inner cylinder between an outer resting position and an inner operative position wherein the push rod acts on the switch to break the current circuit, and wherein a the push rod during displacement to the active position passes and is releasably locked in the active position by being arrested behind a spring member supported on the inner cylinder. The movement of the push rod in a direction towards the resting position is axially limited by an outer cylinder which is journalled about the inner cylinder and the cylinders are inter-locked in the coupled position through the aid of snap-lock means acting between and being encased between the cylinders in their interconnected position.

TECHNICAL FIELD OF INVENTION

The present invention relates to the operating of a switch for manualswitching off of an electric current circuit, and more particularlypertains to an operating means with which, in a case of emergency, thecurrent circuit may be switched off and closed again only through amanual activation of the operating means when the emergency situationhas been remedied. More specifically, the invention providesimprovements on such safety switches in respect of the ability towithstand outer manipulation, and in particular unauthorised dismountingof the installed safety switch.

Herein, the expression “safety switch” refers to a separate operatingmeans by which a switch is operated for switching off an electric powercircuit.

TECHNICAL BACKGROUND

Safety switches of various types are previously known, by which arestorable switch is operated in emergency situations for disconnectingan electric circuit by hitting or pressing a press button of the safetyswitch. Connection may be restored through a pulling or turning motionof the button to overcome or avoid the effect of a spring or otherlocking element that engages a movable portion of the safety switch,arranged for securing the disconnected condition.

A frequent problem in connection with safety switches that are installedin environments that are non-restricted and thus available for thepublic is damages caused on the safety switch. Such damages may involveunauthorised dismounting of the push button or of the entire safetyswitch, or manipulation of its function. In all cases the safety switchloses its ability to prevent a dangerous outcome in case of amalfunction of an electrical apparatus. A manipulation of the functionof the safety switch may not necessary be detected before the emergencysituation arises, thus adding to the risk of a hazardous outcome.

A technical problem in respect of the above said is to design the safetyswitch in such way, that after installing,. it will be impossible todismount or manipulate the safety switch without leaving visible damageson the exterior of the safety switch.

OBJECT OF INVENTION

It is thus a primary object of the invention to provide a safety switchhaving mounting means that are inaccessible from the outside when thesafety switch is assembled.

SUMMARY OF THE INVENTION

According to the invention there is provided an operating means foroperating a switch in an electric current circuit, comprising an innercylinder connected to the switch, a push rod being axially displaceablerelative to the inner cylinder between an outer rest position and aninner active position wherein the push rod effects the switch to breakthe current circuit, and under displacement to the active position thepush rod passes and releasably locks into the active position byengagement with a spring member supported by the inner cylinder, and apush button is connected to the push rod for moving the push rod betweensaid positions. An outer cylinder limits the axial travel of the pushrod towards the rest position. Upon assembly, the outer cylinder isjournalled about the inner cylinder and the cylinders are then mutuallyrotated to a coupled position in which the cylinders are inter-locked bya snap-lock means that is encased by the superimposed outer cylinder inthe assembled position and operative for preventing a relative rotationof the cylinders in the locked position.

Other objects and advantageous embodiments of the invention are furtherdefined in the subclaims and the following description of exemplifyingembodiments, respectively.

DRAWINGS

Below, the invention will be more closely described with reference madeto the accompanying drawings, wherein

FIG. 1 is an exploded view showing the separate elements of the safetyswitch in a non-assembled position, and

FIG. 2 is an axial cross sectional view through the separate elements ofthe safety switch, also shown in the non-assembled position and with apush rod incorporated in the safety switch shown also in a transverseside view.

DETAILED DESCRIPTION

Referring to FIGS. 1 and 2 there will be described a safety switch 1according to the invention in a currently preferred embodiment.

In this embodiment, the safety switch 1 is designed to operate a contactblock 2, which is controlled by the safety switch to break, in case ofan emergency, an electric power circuit to which the contact block isconnected. A carrier 3 that is formed to receive and hold the safetyswitch, e.g. by way of a spring 4 supports the contact block. The spring4 is inserted into slots 4′ and 4″ arranged on the contact block carrier3 and the safety switch 1, respectively, and acting to hold theseaxially and against relative rotation. The carrier 3 and the contactblock 2 are preferably arranged within a panel or front plate (notshown) of an apparatus box or the like, whereby the safety switch 1 ismounted through a hole in the panel and fixed by a nut 5. In theassembled position the nut is screwed onto an inner cylinder 6 whichextends through the panel and into the contact block carrier 3.

A push rod 7 is arranged so as to be axially displaceable in the innercylinder 6. In a case of emergency the push rod is operated via a pushbutton, further described below, to press a switch 8 on the contactblock in order to break the power circuit. This position refers to theoperative or activated position of the push rod or the safety switch,respectively, in this disclosure.

On its outside, the push rod 7 is formed with two diametrically opposingshoulders, of which only one shoulder 9 is shown in FIG. 1. When thepush rod is moved to the active position, said shoulders pass through aU-shaped spring member 10 to be releasably arrested behind the legs ofthe spring member 10. The spring member 10 is supported by the innercylinder 6 to extend transversely relative to, and on opposing sides ofthe push rod 7, and is pushed tangentially into the cylinder 6 to berested in grooves 11 arranged in a collar section 12 of the cylinder 6.In the shown embodiment the spring member 10 is shown to be extendedtangentially in relation to the push rod 7, having a circular crosssection, and being fixed in the rested position by an outer cylinderwhich is described below.

The push rod 7 has a collar 13 extending radially outside the shoulders9. In the non-operative position (rest position), the collar 13 abuts aflange arranged on the inside of an outer cylinder 14.

When assembled, the outer cylinder 14 is shaped to be superimposed orjournalled about the inner cylinder 6 so as to extend concentricallyabout the outside of this, preferably for the whole axial length of thecollar section 12 of the inner cylinder 6. The cylinders are mutuallyconnected through a bayonet mount, for which purpose shoulders 15 arearranged outwardly on the collar section 12 of the inner cylinder 6. Theshoulders 15 are inserted into sockets 15′ arranged on the inside of theouter cylinder 14, and are brought to an end position in the sockets 15′upon relative rotation of the cylinders whereby the cylinders areaxially connected. A snap lock means is arranged to act between theinner surface of the outer cylinder 14 and the outer surface of theinner cylinder 6. The snap lock means comprises a flexible tongue 16formed on the outside of the inner cylinder. When the shoulders 15 arerotated to the end position of the bayonet mount, the tongue 16 snapsinto a groove 17, see FIG. 2, formed on the inside of the outer cylinder14. Thus, when the cylinders are mutually connected the snap lock meansis encased between the cylinders and may only be accessible by tearingapart the outer cylinder 14. The tongue 16 prevents relative rotation ofthe cylinders 6 and 14 in the position where the tongue has snapped intothe groove 17, so that the cylinders also are rotationally fixed.

The shoulders 15 of the inner cylinder 6 and the sockets 15′ of theouter cylinder 14, respectively, are preferably designed to allow, onlyin a certain rotational position, the outer cylinder to be pushed ontothe inner cylinder. Such restriction may be applied e.g. by anon-symmetrical positioning of shoulders and sockets in the peripheriesof the two cylinders, or by arranging one or more of the shoulders andsockets with a different length than the other shoulders/sockets.Furthermore, the tongue 16 may as in the shown embodiment becircumferentially oriented on an inner end surface of the inner cylinder6, and the groove 17 may be realized as a recess in the front face of ashoulder 17′, against which said end of the inner cylinder is inabutting contact in the coupled mode of the cylinders. Alternatively,the snap lock means may also comprise several flexible tongues orgrooves 16 and 17, respectively.

The safety switch 1 according to the shown embodiment is configured inthe way described below to be freely adapted for a pulling operation ora turning operation when the push rod 7 is to be reset to its restposition.

Before connecting the inner and outer cylinders 6 and 14, respectively,the push rod 7 is fitted into the inner cylinder. To this end the pushrod is provided with a guide in the form of an axially runningprojection 18 formed on its outside. During assembly the projection 18is fitted into one of two alternative grooves 19 or 20 running axiallyon the inside of the inner cylinder 6. The groove 19 is dimensioned toreceive the projection 18 substantially rotationally fixed therein,while the groove 20 is configured to receive the projection for alimited rotation therein.

It will be appreciated that when the push rod is mounted for guidance inthe groove 19 resetting of the push rod 7 occurs in an axial pullingmotion against the action of the spring member 10. When the push rod ismounted for guidance in the groove 20 resetting of the push rod 7 occursin a rotational movement in which the shoulders 9 pass freely of therespective legs of the spring member 10.

In an outer end, the push rod 7 is provided with a number of heels 21.When assembled, the heels 21 engage shoulders that are arranged on apush button 22 further described below.

The push button 22 is shaped as a cup, formed internally with couplingmeans by which the push button is connected to the push rod 7.Alternatively, the push button may be formed with a large end planehaving a lower side from which a sleeve is depending and arrangedinternally with coupling means for connection to the push rod 7. In bothcases, the end plane of the push button is formed with a seat forreceiving a cover plate 23, screwed or snapped into the seat so as to belevelled with or positioned below the end plane. A sealing ring 24 may,if necessary, be fitted to rest in a groove inwardly of the cover plateto prevent dampness from getting into the push button.

The connection between the push rod 7 and the push button 22 is realizedthrough the angularly spaced heels 21 of the push rod, in the connectedposition resting against the top of correspondingly formed shoulders 25extending radially inwardly from the inner periphery of the sleeve orcup-shaped wall of the push button. Upon assembly, the push button ispushed over the end of the push rod by turning these mutually so thatthe shoulders 21 may pass in recesses 26 formed between the shoulders25, whereupon the push button is rotated in order to bring the shoulders21 and 25 into engagement.

A washer 27 secures the connection between the push rod 7 and the pushbutton 21. The washer 27 comprises a ring, from which flexible legs 28,depending in axial direction, are formed in the tips thereof withhook-shaped gripping means 28′ protruding radially outwards from thetips. In the secured position, the gripping means are arrested behindshoulders 26′ formed in the recesses 26. Thus, in the snapped-inposition of the washer, the legs 28 extend axially in the recesses 26,and prevent a rotation of the push button relative to the push rod. Atthe same time, the washer 27 is axially fixed in the push button by theengagement of the gripping means 28′ behind the shoulders 26′ of therecesses 26, so that the ring-shaped section of the washer axiallysecures the connection between the push button 22 and the push rod 7.

A coil spring 29 is provided to act between the outer cylinder 14 andthe push button 22, so that the push rod 7 is biased in the direction ofthe resting position. For this purpose, the sleeve or cup-shaped portionof the push button 22 is formed with an annular and concentric groovefor receiving the coil spring 29. In its ends, the coil spring 29 isformed with means, not showed in detail, e.g. bent or angular sectionsfor non-rotational engagement with the cylinder 14 and the push button22, whereby the spring also acts to rotate the push rod back to aninitial position after resetting through a turning operation. The grooveis dimensioned to allow journalling of the push button on the outercylinder 14 in the assembled position, whereby a ring-shaped seal 30 maybe applied for sealing between the outer cylinder and a peripherallyouter wall of the groove. Hereby it may be secured that dampness isprevented from getting in between the push button and the outercylinder.

In the assembled position, the outer cylinder 14 extends with the innerend thereof in a plane coincident with the lower edge of the collarsection 12 of the inner cylinder 6. In this position, a sealing ring 31may be fitted between the panel, cover plate or similar facing of thecontact block, and the inner end of the outer cylinder, to make surethat dampness is prevented from getting in between the inner and outercylinders 6 and 14, respectively.

In a preferred embodiment the push rod 7 is a hollow member, and thecover plate 23 translucent, so that a light source arranged in thecontact block or the switch may be visible through the safety switch 1.For this purpose, the push rod is advantageously formed in its inner endwith one or more transverse beams, e.g., not shown in detail, forengagement with the switch of the contact block.

In the above description of an embodiment there has been suggested anoperating means for operating a switch in an electric current circuit,or a safety switch, wherein elements are designed to co-operate forenclosing and preventing unauthorised access to the interlocking meansarranged for connecting the elements in the assembled position of thesafety switch. A central feature of the invention is the encasedsnap-lock connection between the inner and outer cylinders,respectively. Upon assembly, the snap-lock means allow the relativerotation of the cylinders into an interlocking position, wherein thecylinders are non-rotationally interconnected so that access to theconnection is possible only by tearing apart the outer cylinder. Anothercentral feature of the invention is the encased snap-lock connectionbetween push button and push rod, and a further advantageous feature isthe optional assembly of the push rod for a pulling or a turningoperation, when the safety switch is to be reset.

In this embodiment, the snap-lock means 16, 17 are designed to beeffective in a peripheral area between the inner cylinder 6 and theouter cylinder 14, and arranged to operate in axial planes of thecylinders.

Without specifically being shown herein, it is appreciated that asnap-lock means may alternatively be realized as a tongue formed on theinside of the inner cylinder, adapted to lock by snapping into a grooveformed on the inner periphery of the outer cylinder upon relativerotation of the cylinders to an end position. In both cases, thesnap-lock means operate with a tangentially directed component force, inthe first case between axially directed surfaces and in the second casebetween radially directed surfaces, to prevent a relative anddisconnecting rotation between the outer and inner cylinders afterassembly.

The object of the invention is achieved by the unreleasablyinterconnected cylinders 6 and 14, the locking connection of which isinaccessibly enclosed between the cylinders in the locking position. Anymanipulation that would result in affecting the current breakingfunction of the safety switch requires an irreparable damage to becaused on the outer cylinder 14.

The effect of the invention is furthermore improved by the likewiseinaccessibly enclosed connection between the push button 22 and the pushrod 7, the separation of which may only be effected through anirreparable damage caused to the cover plate 23 and the locking washer27.

An advantageous feature of the invention is the freedom of choicebetween a pulling or turning operation in order to reset the push rod,made possible by the alternative reception and guide positions 19 and20, respectively, of the inner cylinder.

Furthermore, the safety switch according to the invention is, in itsentirety, sealed against intruding dampness or dirt when mounted out ofdoors or in aggressive environments, and it is designed for passage ofthe light from a light bulb or light diode, arranged in the switch.

The elements and details incorporated in the safety switch arepreferably formed of synthetic materials with high resistance againstextreme temperatures and chemically aggressive substances.

What is claimed is:
 1. Operating means for operating a switch in anelectric current circuit, comprising an inner cylinder connected to theswitch, a push rod axially movable relative to the inner cylinderbetween an outer resting position and an inner active position whereinthe push rod acts on the switch to break the current circuit, andwherein the push rod during movement to the active position passes andis releasably locked in the active position through the engagement witha spring member supported on the inner cylinder, said operating meansfurther being provided with a push button connected to the push rod foroperation of the push rod between said resting and active positions,wherein the movement of the push rod in a direction toward the restingposition is axially limited by an outer cylinder, which upon assembly isjournalled concentric about the inner cylinder whereafter the cylindersare mutually rotated to a locking position, and wherein the cylindersare unreleasably inter-locked through a snap-lock means encased by thesuperimposed cylinders and effective for preventing the relativerotation of the two cylinders in the inter-locked position.
 2. Operatingmeans according to claim 1, wherein the snap-lock means is operable witha tangentially directed component force between axially directedsurfaces of the inner and the outer cylinders, respectively. 3.Operating means according to claim 2, wherein the snap-lock meanscomprises a tongue forming part of a bayonet mount, said tongue snappinginto a groove when the bayonet mount is rotated to an end positionwherein the cylinders are interconnected, wherein the tongue and thegroove are circumferentially oriented and the tongue is formed on aninner end surface of the inner cylinder and the groove is formed on afront face of an inner shoulder of the outer cylinder, so that thesnap-lock means is encased between the cylinders in their interconnectedposition.
 4. Operating means according to claim 1, wherein the snap-lockmeans is operable with a tangentially directed component force betweenradially directed surfaces of the inner and outer cylinders,respectively.
 5. Operating means according to claim 4, wherein the pushbutton comprises a cylinder sleeve concentrically surrounding the outercylinder in the assembled position, a first sealing ring being fittedbetween the sleeve and the cylinder, a second sealing ring beingarranged inwardly of a cover plate attached in the end plane of the pushbutton, and a third sealing ring being arranged between the outercylinder and the switch, or a panel arranged outwardly of the switch, sothat the operating means is completely sealed from intruding thedampness or dirt.
 6. Operating means according to claim 4, wherein thepush rod is a hollow member, and the cover plate is translucent. 7.Operating means according to claim 1, wherein the push rod on itsoutside is formed with two projecting, diametrically opposed shoulderswhich upon operation of the push rod to its active position arereleasably arrested behind legs of the spring member, the spring memberbeing supported on the inner cylinder to extend transversely to the pushrod and on each side thereof, whereby the push rod is released from theactive position by a pulling operation of push button toward the restingposition of the push rod and against the force of said spring member. 8.Operating means according to claim 7, wherein the push rod in itsperiphery is provided with an axially extending projection and whichupon assembly of the operating means alternatively is inserted into oneof two grooves formed on the inside of the inner cylinder and extendingaxially therein, the peripheral length of one of said grooves beingadapted for non-rotationally receiving and guiding of the push rod, andthe peripheral length of the other groove being adapted to receive andguide the push rod for limited rotation therein.
 9. Operating meansaccording to claim 1, wherein the push rod on its outside is formed withtwo projecting, diametrically opposed shoulders which upon operation ofthe push rod to its active position are releasably arrested behind legsthe spring member, the spring member being supported on the innercylinder to extend transversely to the push rod and on each sidethereof, whereby the push rod is released from the active position by aturning operation of the push button for releasing the shoulders frombeing arrested behind the legs of said spring member.
 10. Operating,means according to claim 1, wherein the connection between the push rodand the push button comprises a bayonet mount, which is locked in theinterconnected position by a washer formed to be inserted below thecover plate, the washer having snap-lock means that snap onto shouldersformed internally in the sleeve of the push button, whereby the snaplock means of the inserted washer prevents relative rotation between thepush button and the push rod.